1. Field of the Invention
The present invention relates to a multi-cylinder rotary compressor provided with an improved compression mechanism, and refrigeration cycle equipment using the multi-cylinder rotary compressor for making a refrigeration cycle.
2. Description of the Related Art
Refrigeration cycle equipment comprising a refrigeration circuit uses various types of compressor. For example, an air-conditioner often uses a multi-cylinder rotary compressor, or a two-cylinder compressor. Such a type of compressor has a sealed case housing a motor unit and compressor mechanisms. The motor unit and compression mechanisms are connected through a rotary shaft.
In the above compression mechanism, a rotary shaft comprises a main shaft pivotally fixed to a main bearing, a countershaft pivotally fixed to a sub-bearing, crankshafts which are eccentrically provided between the main shaft and countershaft, fitted with rollers, and a connecting part connecting the crankshafts. The crankshafts and rollers are housed eccentrically rotatable in a cylinder chamber formed inside a cylinder.
In other words, two crankshafts are provided in the main shaft and countershaft. Two cylinders, having cylinder chambers for housing the crankshafts and rollers, are provided. An intermediate partition board is inserted between the cylinders. The connecting part provided between the crankshafts faces the intermediate partition board.
In a multi-cylinder rotary compressor, it is desirable to decrease the diameter of a crankshaft, which is the largest in the sliding part of a rotary shaft, decrease friction loss, and increase efficiency. At the same time, it is recommendable to decrease the height (axial length) of a cylinder, and increase the eccentricity of a crankshaft, in order to decrease sliding loss.
Usually, the main shaft and countershaft forming the above rotary shaft are formed to have the same radius Rm. Assuming the radius of the crankshaft to be Rc and the eccentricity of the crankshaft to be 2, the following formula is established. The diameters of the crankshaft and cylinder chamber can be decreased, and the above advantageous condition can be obtained.Rc<Rm+e 
The problem is the axial length L of the connecting part provided between the crankshafts, and the axial length H (cylinder thickness) of the roller fitted to the crankshaft, which are necessary for fitting the roller to the crankshaft. For example, the axial length L of the connecting part is set smaller than the axial length H of the roller (L<H).
In this case, according to the above relationship (L<H), even if the roller can be inserted from the end face of the countershaft and the connecting part can be connected to the crankshaft provided in the countershaft, when the inserted end face of the roller contacts the end face of the crankshaft provided in the main shaft, the other end face of the roller opposite to the inserted end is positioned oppositely to the crankshaft provided in the countershaft. In other words, the inserted end face of the roller contacts the end face of the crankshaft of the main shaft before the roller does not completely come out of the crankshaft of the countershaft, and the roller cannot be fitted to the crankshaft of the main shaft.
Jpn. Pat. Appln. KOKAI Publication No. 2003-328972 discloses a technique of decreasing the diameter of a countershaft to be smaller than a main shaft, contracting the outer periphery of the side opposite to an eccentric shaft in the crankshaft, from the outer periphery of the main shaft, providing a part having a diameter smaller than the outside diameter of the main shaft in a connecting part (a joint), and making the axial length of the small diameter part greater than the axial length of the roller fitted to the crankshaft of the main shaft.
Jpn. UM Appln. KOKOKU Publication No. 55-48887 discloses a crankshaft comprising a columnar part in which a connecting part formed between adjacent crankshafts (crankpins) is concentric with a rotary shaft line, and smaller than the outside diameter of the crankshaft; and a connecting wall part which is formed on both end faces of the columnar part, and has a cross section which is overlapped when the columnar part and crankshaft are overlapped in the axial direction of the rotary shaft.